Which of these was the largest and most constant issue facing the united states during the era of "manifest destiny? " a) whether labor unions would be allowed to form b) whether states would allow women the right to vote c) whether indians would be relocated to north carolina d) whether slavery would spread across the united states

The correct answer is D. The largest and most constant issue facing the United States during the era of "Manifest Destiny" was whether slavery would spread across the United States.

Explanation:

In the mid-nineteenth century, expansionism, especially southward toward Cuba, also faced opposition from Americans trying to abolish slavery. As more territories were added to the United States in subsequent decades, "widening the area of freedom" in the minds of southerners also meant broadening the institution of slavery. This is why slavery became one of the central issues in the continental expansion of the United States before the Civil War.

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